As is well known to any person skilled in the art, there are both axial and rotational relative movements between the rod or spindle and housing or barrel of a conventional rail vehicle slack adjuster of the axial type at each and every brake operation. This means that the required sealing between the rod and the housing is exposed to great wear, not the least in view of the extremely harsh environment underneath a rail vehicle, where the slack adjuster is mounted.
A typical prior art sealing in the housing may consist of one or more internal sealing rings engaging the rod. These sealing rings may be made of a plastic material in order to withstand the wear better than rubber rings. The result is, however, not statisfactory in some instances when the sealing after a certain period of operation is not tight any more and allows water and contaminants to enter the interior of the slack adjuster resulting in rust problems and eventually function disturbances.